This invention relates to the recovery of energy from geothermal brines and other hot water sources, and is particularly concerned with a process and system of the aforementioned type, employing direct contact heat exchange between the hot brine or hot water feed, and a working fluid, wherein the heated working fluid is expanded to produce work, and the expanded and discharged working fluid is recycled to the heat transfer column, and further providing for working fluid recovery under conditions to afford minimum working fluid loss and maximum energy extracted from the expander.
In prior art processes and systems for recovery of energy from geothermal brines and other hot water sources, employing heat exchange between the hot brine or hot water, and a working fluid, there has been no recognition heretofore of the problem of obtaining a heat balance in the heat transfer column with close temperature differentials or .DELTA.t's between brine or water and working fluid, to obtain maximum efficiency. The prior art also has failed to recognize the problem of working fluid loss in uncondensible gases which come into the system particularly with the hot brine or hot water and which must be vented. Further, the prior art has failed to provide for the problem of working fluid loss in exit brine or hot water from the heat transfer column, and recycle of such recovered working fluid to the heat transfer column.
It is accordingly a chief object of the invention to provide a process and system for recovery of energy from geothermal brines and hot water sources by operation of a heat transfer column preferably providing direct heat transfer between the hot brine or hot water, and a working fluid, under conditions of operation particularly with respect to pressure in the heat transfer column and temperature of the hot brine or hot water feed, in relation to the critical pressure and temperature of the working fluid, to allow maximum energy recovery for any individual working fluid. A further object is the provision for recovery of additional energy by expanding the cold brine or water from the bottom of the heat transfer column. A still further object is the provision in the procedure and system, for removal of working fluid from the exit brine or water from the column and recovery of such working fluid. An additional object is the control of the working fluid concentration in the uncondensible vent gas from the system to obtain an economic balance between energy recovery from the process and system, and working fluid loss in the uncondensible vent gas. Yet another object is to operate under conditions to substantially reduce the quantity of vent gas containing working fluid that vents from the system to thereby minimize working fluid losses, while maximizing energy recovery. Still another object is the provision of simple and efficient procedure for removing the major portion of uncondensible gases from the incoming brine or hot water source prior to introduction into the heat transfer column. Another object is the provision of procedure and a system for converting H.sub.2 S in such removed uncondensible gases to sulfur. Another object is to use the H.sub.2 S converting system to also handle condensed water and any vent gas from the accumulator, thus reducing air and water pollution problems and recovering good quality water.